1. Field of the Invention
The present invention relates in general to providing operator access to elevated portions of mobile crane systems. More specifically, the invention relates to an access system including a staircase that is selectively attachable to a deck of a mobile crane system for providing access to an operator's cabin throughout the use of the crane system at a job site.
2. Description of the Related Art
Mobile crane systems are often designed to operate both as cranes for lifting loads and as vehicles capable of moving in normal road traffic. These mobile crane systems generally include an undercarriage supporting a driver's cabin at a forward end thereof, from which a driver operates a steering wheel, turn signals, and the normal implements for operating a vehicle in traffic. Behind the driver's cabin, an upper carriage is often rotatably mounted on a deck of the undercarriage. The upper carriage generally includes a boom that can be lifted and lowered, various winches and hoisting cables, and on operator's cabin from which an operator controls the boom, winches, and other components of the crane system. The operator's cabin is generally elevated and positioned on a lateral side of the upper carriage to provide visibility for the operator and to provide space for the boom to be lowered for traveling.
A vertical ladder is often built into the undercarriage, or provided with the crane system as a pivot attachment to the undercarriage. These vertical ladders generally do not extend a significant lateral distance from the undercarriage, and thus, do not pose a hazard to road traffic adjacent the mobile crane system while travelling. The vertical ladders are provided in various locations including directly under, or slightly forward of a door to the operator's cabin. To gain access to the operator's cabin, an operator must climb the vertical ladder, and rely on various handholds on the deck and on the exterior of the operator's cabin for support. From the vertical ladder, the operator must lean right to slide open the door, and either pull himself or swing himself into the operator's cabin. Opening the door often involves shifting the operator's center of gravity well to the side beyond the deck of the crane or the edge of the support ladder to provide the momentum to open the door. During this motion, the operator is frequently standing on the outer edge of the deck or on a rung of the ladder while using one hand to hold onto a fixed handhold at a different location, with or without gloves. At times, operators may use both hands to open a door when the door does not open easily. The operator is susceptible to falls while opening the door or entering the cabin, as his full weight is borne on one of the hand holds at a time when he is generally off balance transitioning into the operator's cabin or leaning against the door to open it.